A video apparatus often comprises a receiver which is meant to produce a video signal (e.g. an analogue video signal according to the NTSC or PAL standard) based on an RF signal received from a remote broadcaster.
It becomes common practice nowadays to provide such a video apparatus with an encoder (e.g. a MPEG encoder) in order to convert the received video signal into an encoded stream (e.g. a MPEG encoded digital stream).
This is useful notably to record the received video sequence as a digital stream on a medium, for instance on a DVD or on a hard-disk drive located in the apparatus.
A problem in such a system is that the received video signal may be noisy and may lead therefore to an encoded stream with defects (artefacts). These defects clearly appear as macro-blocks when the video sequence coded by the encoded stream is displayed.
In order to avoid appearance of these artefacts, the video signal is sometimes processed in a specific way; for instance, the video signal is processed through a low-pass filter before being encoded. However, this specific processing generally has some limitations or drawbacks; for instance, the low-pass filter removes the details of the video sequence (high frequency part of the video signal), even when the received video signal has a good quality (good signal-to-noise ratio) and would lead to correct encoding with a weaker low-pass filter keeping more details.